The invention relates to an arrangement for the electrothermal treatment of the human or animal body, in particular for the electrocoagulation or electrotomy.
The use of high-frequency alternating currents in the frequency range of 300 kHz to 2 MHZ for tissue coagulation and tissue separation has long been known in the field of surgery, resulting in the treated tissue being coagulated or vaporized, which is referred to as electrocoagulation or electrotomy. A distinction must be made here between the monopolar and the bipolar HF thermotherapy.
For the monopolar thermotherapy, an electrodexe2x80x94also referred to as the neutral electrodexe2x80x94is configured as a large-surface patient lead and is installed near the place of incision on the patient. The shape of the actual working electrodexe2x80x94referred to as the active electrodexe2x80x94is adapted to the respective application. Thus, large-surface sphere, disk or needle electrodes are used for the tissue coagulation, whereas thin lancet or loop-type electrodes are used for tissue separation.
In the bipolar HF thermotherapy, on the other hand, both electrodes are arranged in close proximity to the place of incision, so that the effect of the alternating current is limited to the area immediately surrounding the place of incision, thereby resulting in a high degree of safety for the patient and the user since accidents caused by capacitive leakage currents or burning at the neutral electrode can no longer occur. Another advantage of the bipolar HF thermotherapy consists in the considerably lower load resistance of the tissue between the two electrodes, which permits a reduction in the necessary generator output while maintaining the thermal effect.
Based on the position of the electrodes, the HF thermotherapy can furthermore be divided into the surface coagulation on the one hand and the depth coagulation on the other hand.
The bipolar technique uses two parallel-arranged tactile electrodes for the surface coagulation, which are placed onto the tissue surface. As a result of this, the tissue underneath is heated, owing to the flow of current, and is thus coagulated.
The use of needle, lancet, or loop-type electrodes for the monopolar electrotomy is known in the field of depth coagulation. Electric arcs must be generated for this on the active electrode in order to vaporize the tissue, positioned in front of the active electrode, thereby realizing a tissue cut. This is relatively simple with the monopolar technique because only a specific field strength is required to trigger a spark discharge at the active electrode. The bipolar technique makes higher demands on the design of the electrode configuration since the physical processes in this case cannot be controlled as easily. That is why only a few bipolar electrode arrangements for the depth coagulation are known, e.g. the bipolar needle electrode, which is suitable, among other things, for the myoma therapy. This known bipolar electrode arrangement consists of two parallel-arranged needle electrodes that are stuck into the tissue, by means of which the tissue between the electrodes is heated as a result of the current flow and is thus coagulated.
However, the known bipolar electrode arrangements for the depth coagulation have the disadvantage that placement of the electrodes through two puncture sites is relatively involved. Furthermore, the predetermination of the field distribution by the user is relatively imprecise because the position of the two electrodes relative to each other generally cannot be specified exactly.
The DE 43 22 955 A1 furthermore discloses the use of laser radiation for the coagulation of body tissue, which laser radiation can be transmitted into the therapy region via a cylindrical optical waveguide, wherein the known optical waveguide additionally permits the transmission of ultrasound energy, so that the two therapy methods of ultrasound tissue separation and the laser coagulation can be combined.
A waveguide is also disclosed in the DE 44 32 666 A1, which makes it possible to transmit high-frequency energy in addition to ultrasound waves and laser radiation, so that the initially mentioned methods of high frequency surgery can be used at the same time as the laser surgery and the ultrasound surgery. For this, the known waveguide has a cylindrical design and additionally comprises two layers of an electrically conductive material for the high-frequency transmission, which layers are also cylindrical and are electrically insulated against each other. Thus, the known waveguide permits the transmission of high-frequency energy from a high-frequency generator, arranged extracorporeal, into the therapy region, but it does not permit the release of the high-frequency energy to the body tissue.
It is thus the object of the invention to create an arrangement for the electrothermal treatment of the human or animal body, which permits an interstitial tissue coagulation by means of a bipolar electrode arrangement and which avoids the aforementioned disadvantages of the known types of arrangements.
The invention includes the technical teaching that a bipolar electrode arrangement is used for the thermotherapy, the two electrodes of which are arranged one after another on an elongated catheter to make it possible to insert the two electrodes jointly into the body through a single puncture site, wherein the two electrodes are connected to the catheter or form a component of the catheter.
Herewith and in the following, the term catheter is understood to have a general meaning. It is not limited to the preferably used hollow-cylindrical arrangements, described in detail in the following, but can also be realized with large arrangements of nearly optional cross sections. Critical to the function according to the invention is only that the two electrodes are inserted jointly into the patient""s body, through one puncture site.
The catheter according to the invention for the first time allows placing the electrodes into deep tissue layers and obtaining a partial tissue coagulation there.
The electrodes in the arrangement according to the invention are connected to a current source that supplies the electrical energy necessary for heating up the tissue. The term current source here is not limited to narrowly defined sources having a constant current, but includes also the preferably used alternating current generators, especially high-frequency generators.
One advantageous variant of the invention provides that the axial distance between the two electrodes can be adjusted, so that the field distribution can be varied. If the insulator length in axial direction between the two electrodes is shorter, for example, than twice the electrode diameter, spherical coagulation necroses can be obtained advantageously, whereas the shape of the coagulation necroses for longer insulator lengths is more oval.
The preferred embodiment of this variant therefore provides that the proximal electrode has a hollow design, at least at its distal end, such that it can accommodate the distal electrode on its inside. The external cross section of the distal electrode is smaller than the internal cross section of the proximal electrode to allow an axial displacement of the distal electrode inside the proximal electrode. It is important in this case for the two electrodes to be electrically insulated against each other in a suitable manner, since the two electrodes can overlap in axial direction. An electrical insulation is provided for this on the inside of the proximal electrode or on the outside of the distal electrode. For example, this insulation can consist of a dielectric coating or an insulating material sleeve, preferably composed of PTFE or polyimidexe2x80x94as in the initially listed reference DE 44 32 666 A1xe2x80x94wherein the cross section for the insulating-material sleeve is preferably adapted to the cross section of the distal or proximal electrode, such that the insulating-material sleeve can be press-fitted to the proximal or distal electrode and is thus fixed on the electrode. Thus, the two electrodes are coaxially arranged and can be displaced against each other in axial direction, so that the field distribution can be changed, wherein a section of the distal electrode in longitudinal direction is held inside the proximal electrode.
In this variant of the invention, as for the other variants of the invention, the two electrodes have a cylindrical cross section, wherein the internal diameter of the proximal electrode for this variant must be larger than the external diameter of the distal electrode, so that the distal electrode can be displaced in axial direction. However, the invention is not limited to cylindrical electrode designs, but can be realized with other electrode cross sections as well. Concerning the function of this variant of the invention, it is only critical that the internal cross section of the proximal electrode is adapted to the external cross section of the proximal electrode in such a way that the distal electrode can be displaced in axial direction inside the proximal electrode in order to change the axial distance between the two electrodes.
In another variant of the invention, the adjustment of the axial distance between the two electrodes is made possible with an elongated carrier element of electrically insulating material, which is arranged such that it can be displaced inside the proximal electrode and contains the distal electrode on the side in its distal region. The proximal electrode is therefore designed to be hollow, at least at its distal end, to be able to hold the carrier element. The internal cross section of the proximal electrode in this case is adapted to the external cross section of the carrier element, such that the carrier element can be displaced in axial direction in order to be able to adjust the axial distance between the distal end of the proximal electrode and the distal electrode, arranged on the carrier element. In this variant of the invention, the distal electrode is attached to the side of the electrically insulating carrier element and can consist, for example, of a ring-shaped, metallic coating or a metallic sleeve, which is pushed axially onto the carrier element during the assembly and is press-fitted to this carrier element.
In accordance with another variant of the invention, the spacing between the two electrodes is specified, to achieve a simple design for the catheter and to ensure a predetermined field distribution. For this, the catheter also has an elongated carrier element of electrically insulating material, with the electrodes fixedly attached to the side in axial direction and at a distance to each other. On the one hand, the carrier element here is used for a mechanical fastening of the electrodes, in order to achieve a predetermined field distribution as a result of the constant distance between the electrodes. On the other hand, the carrier element must insulate the two electrodes electrically against each other and is therefore composed of an electrically insulating material. In the preferred embodiment of this variant, the carrier element has a cylindrical cross section, wherein the two electrodes have a hollow-cylindrical design and are arranged so as to be circumferential with respect to the longitudinal axis of the carrier element. In this case, the electrodes can be deposited, for example, on the carrier element surface as a metallic coating, or they can respectively form a metallic sleeve that is fitted onto the carrier element and is press fitted to it.
In another embodiment of this variant, the electrodes are not fixed axially as a result of being arranged on a carrier element, but through respectively one connecting element between the electrodes, which connects the fronts of the electrodes. In addition to the axial fixation of the electrodes, the connecting element must also insulate the two electrodes against each other and thus consists of an electrically insulating material. The electrodes and the connecting pieces in this case are preferably cylindrical and have the same cross section, so that the outside contour of the catheter is continuous, without projecting edges, at the transitions between the electrodes and the connecting elements. This is very important for the insertion of the catheter into the body of the patient, to avoid unnecessary injuries.
A modified variant of the invention provides for more than two electrodes, which are arranged at a distance to each other in axial direction of the catheter. As described in the above, the electrodes can be attached to the side of an elongated carrier element or, as previously explained, can respectively be separated from each other with the aid of a connecting element of electrically insulating material.
The preferred embodiment of this variant provides that the individual electrode pairs, arranged such that they are distributed axially along the longitudinal axis of the catheter, can be actuated separately and have separate feed lines for this, which are preferably extended out of the body through a hollow conduit inside the catheter and can be connected to an adequate control device that permits an individual adjustment of, for example, current, voltage and/or frequency. As a result of the superimposition of the fields generated by the individual electrode pairs, it is possible in this way to specify the field distribution freely within far-ranging limits, e.g. to destroy as little healthy tissue as possible during an electrocoagulation. In one advantageous modification of this variant, the extracorporeal control device has several storage elements, in which the electrical parameters such a current, voltage and frequency for various field distributions are stored, so that the user must only select the desired field distribution, whereupon the control device then reads out the electrical parameters necessary for reaching this field distribution from the respective storage element and respectively actuates the individual electrode pairs.
Other advantageous modifications of the invention are shown in further detail in the following with the aid of the figures and together with the description of the preferred embodiment of the invention.